Process for coking coal



' May 9, 933.

s. w. PARR Er AL. 1,907,568 l PROCESS FOR COKING COAL Filed Jan. 2l,1929 -2 Sheets-Sheet l ATTORNEYS 2 Sheets-Sheet 2 A rNvENToR JMW E 27317m# ATTORNEYS May 9, 1933. s. w. PARE ET AL PROCESS FOR COKING COALFiled Jan. 2l, 1929 EN@ @wal Patented May 9, 1.93

UNITED STATES PATENT OFFICE SAMUEL-W. PAB/.R AND THOMAS E. LAYNG, OFURBANA, ILLINOIS, ASSIGNORS TO URBANA COKE CORPORATION, OF UR-B WARE:PROCESS FOR COKING COAL Application led January 21, 1929. Serial No.333,814.

This invention relates to an improved process of coking coal, and moreparticularly concerns a coking process Which results in the economicalproduction of an improved and uniform quality of coke, tar and gas fromvarious types of coal.

The primary object ofmost coking processes is the derivation of oneproduct such as gas, coke or tar, from the coal treated, and accordingto Ordinar by-product coking practice, the quality o the remaining orless important products is usually sacrificed to a certain extent. Thecost of producing the desired primary product depends upon many factorssuch as the coking time, the heat required to carry out the cokingoperation, and the quantity and value of the secondary productsobtained. Thus any improved coking process which results in a reductionin coking time and heat consumed While at the same time enhancing thequality and quantity of the by-products obtained, aects very substantialeconomy in the production of the desired primary product.

When coal is subjected to temperatures such that coke is ultimatelyproduced, vapors and gases are driven off, the character of the volatilematter derived at any particular time being dependent upon thetemperature of the fuel at that time and upon other factors such as therate at which the coal is heated andthe temperature of the coke ovenWalls or other surfaces or materials with Which the evolved vapors comeinto contact. The hydrocarbon vapors evolved from coal at any giventemperature are readily decomposed or cracked when subjected totemperatures higher than those at which they are evolved, and inordinary by-product practice the valuable constituents thereof arelargely lost or broken down into less valuableproducts during the cokingprocess due to the prolonged contact of the evolved vapors with the hotwalls of the coking ovens, or with masses of hot coke adjacent the ovenwalls.

According to ordinary by-product coking practice, raw coal is placedWithin an oven or retort and the Walls thereof are heated until theentire coal charge is converted into coke. The coal in contact with theoven walls is first heated to a temperature at which it becomes plasticand is then converted into coke, and the plastic. condition slowlyprogresses inwardly into the coal charge in a thin layer or envelope.The layer of coke adjacent the oven Walls acts as an insulating barrierto the transmission of heat from these Walls to the central portion ofthe fuel charge, thus appreciably delaying the coking operation andnecessitating the use of excessively high oven Wall temperatures. Aportion of the hydrocarbon gases, which are largely evolved at or abovethe temperature of plasticity or critical temperature, condenses intotar on the inner face of the plastic layer or envelope'on coming intocontact with the relatively cold raw coal adjacent and Within theplastic layer. This condensation of the hydrocarbons renders the plasticenvelope comparatively impermeable to the passage of evolved gases, anda large proportion of the hydrocarbon vapors are accordingly forced topass upward outside of the plastic la er through the hot coke and alongthe hig ly heated oven Walls. This passage of the ANA, ILLINOIS, ACORPORATION OF DELA- i evolved vapors in Contact with highly heatedmaterials and surfaces Within the oven, not only results in the abovedescribed undesiraf ble cracking or decompositioniof the hydrocarbons,but materially delays the coking process. Since the evolved vapors arelargely excluded from the central mass of raw coal, the transmission ofheat to this coal by convection through the vapors is prevented. Thetar4 obtained in ordinary by-product practice comprises a mixture ofhigh temperature and low temperature tar for the reason that some of thehydrocarbon vapors have been subjected to very high temperatures in theovens,'whereas a relatively small portion of the vapors have passed offthrough ,the raw coal at the center of the oven without being subjectedto decomposing temperatures.

According to the present invention, it is proposed to utilize toadvantage the exothermic heat available in the coal in order that theextraneous heat consumed as well as the coking time may be materiallyreduced. The improved process avoids the decomposition or cracking ofthe evolved vapors during the coking operation and so enhances thevalues of the by-products derived. The process of the invention resultsin the production of `an improved coke of uniform quality which issuitable for metallurgical or domestic uses, and further produces a richgas and a tar of uniform composition containing valuable constituents.Illinois or other so-called noncoking coals may be treated b the processofthe present invention, as we as the various coking coals.

Our improved method of treating the coal comprises first heating thecoalsubstantiall out of contact with the atmosphere and pre erably,although not necessarily, with agitation, in such a manner thatuniformly throughout, the average temperature of the coal is fairlyclose to but below the critical temperature thereof, that is, thetemperature at which the coal first softens and becomes plastic. Thetemperature to which the coal 1s preheated is hereinafter more fully eX-plained. The preheated coal is then confined in an oven and sufficientextraneous heat is supplied thereto to cause the coal tem erature toincrease quickly to and through tli stage and up to a final temperatureof from 650 to 850 C., or higher. The preliminary heat treatment of thecoal serves to condition it for the carbonization process which is tofollow. During this preliminary heating, free moisture is driven olf andcertain reactions take place which result in the removal of deleteriousoxygen and oxygen compounds such as H2O and C02. The specific heat ofgases such as H2O and CO2 is rather high, and the evolution andelimination thereof during the preheating stage therefore prevents thesubse uent loss of an a preciable amount of heat t rough the evolutionof these gases during the carbonization process. If the reactions justmentioned were allowed to occur simultaneously with the reactions of thecarbonization sta e, the would have the effect of weakening t e bin ingmaterial to such an extent that coke of an inferior quality would beproduced.

Due to the preliminary neat treatment the portion of the fuel chargeadjacent the oven walls is quickly carried up to the criticaltemperature and into the asty stage, and the exothermic reactions whichtake place during the pasty stage result in the liberation of aconsiderable amount of heat which is transmitted to the adjacentportions of the fuel charge, thus causing the rapid autogenousprogression of the pasty stage throughout the entire mass of the charge.The preliminary heat treatment of the coal promotes and makes possiblethis autogenous progression of the pasty stage for several reasons."Since v the temperature of the coal is raised during the lpreheatingprocess, to a value comparative y close to the critical temperature, theamount of heat required to bring the fuel to e pasty.

the critical temperature is comparatively small, and is well within therange of the available exothermic heat. Since certain gases having highvalues of s ecitic heat such as H2O and CO2 have been ellminated duringthe preheating operation, the extraneous andl exothermic heat availablein the coking ovens is not carried away by these gases, and is directlyavailable for raising the coal temperature to and above the criticalvalue. Further, since the fuel charge is preheated throughout its mass,there is little or no condensation of the hydrocarbon vapors evolvedfrom the coal adjacent the oven walls when these vapors come intocontact with the central portions of the charge, and the formation of amore or less impermeable plastic envelope is thereby avoided. Thus thehydrocarbon vapors are not confined to the outer ortions of the chargebut vilow through t e entire mass thereo quickly carrying heat to thecentral portions of the charge and thereby accelerating the autogenousprogression of the pasty stage.

The rapid progression of the pasty stage throughout the mass of coalcharge prevents the formation of a concentrated and comparativelyimpermeable plastic envelope in the charge and the hydrocarbon vaporsare evolved simultaneously throughout the entire fuel mass and escapethrough the entire charge rather than along the oven walls. Theenetration of the evolved gases through the c arge serves to aid inconducting heat to all portions thereof at a rapid rate, and thepenetration of heat into the charge is further accelerated by thecomparatively good heat conducting properties of the plastic coal. Sincethe coal charge is rap1dly heated throughout to a temperature at whichthe evolution of gases begins, the gases are neither condensed nordecomposed or cracked during their passage through the fuel and out ofthe oven, and the tar and other products obtained are therefore of asuperior quality. The rapid heating of the fuel charge through theplastic stage causes the shrinkage t ereof much sooner than Would be thecase if raw coal were introduced directly to the ovens, and thisshrinkage prevents the sticking of the coke and consequent difficultiesin discharging the ovens.

The amount of heat available in the ovens for raising the coaltemperature to and above the critical value and into the plastic zone isfurther increased by the fact that reactions of a secondary nature arelargely avoided. It has been found that whereas primary reactions ordecompositions taking place during the carbonization of coal areexothermic, secondary reactions are generally endothermic, resulting inthe absorption of heat. Since the process of the present inventionavoids such secondary reactions as the cracking of the evolvedhydrocarbon vapors, the

heat ordinarily absorbed by these reactions is made available forraising the temperature of the fuel.

In accordance with the process of the present invention, the temperatureto which the present invention contemplates preheating the coal to atemperature such' that the exothermic heat of the coal, when evolved, iscapable of further raising the coal temperature from the preheatingvalue to a temperature, preferably above the critical temperature, andhigh enough to ensure the autogenous progression of the exothermicreactions throughout the charge. As soon as the coal in contact with theoven walls reaches the temperature at which the exothermic reactions areinitiated, the exothermic heat liberated thereby brings the adjacentcoal to and above the temperature of exothermicity, and this actioncontinues rapidly throughout the mass of the charge. The term exothermicheat, as employed herein, has reference to the excess of heat evolved byexothermic reactions over heat absorbed by endothermic reactions. 'Ilheamount of exothermic heat liberated varies somewhat in different coals,but in general, the excess of exothermic heat over heat absorbed byendothermic reactions throughout the period when exothermic reactionsare most in evidence has been found to be in the neighborhood of from to100 B. t. u. per pound of coal. The specific heat of coal at thetemperatures under consideration is in the neighborhood of .34, andaccordingly, 65 B. t. u. will raise the coal temperature approximately106 C. and 100 B. t. u. will raise the coal temperature approximately163 C. The exothermic reactions ordinarily take place at temperaturesslightly above the critical temperature of the coal, and it is thusevident that a preheating temperature approximately 100 to 160 C. belowthe critical temperature may be Sullicient to cause the above describedautogenous progression of the exothermic reactions to the center of thecoal charge.

The temperature ranges through which different types of coal remainplastic vary considerably. Thus this range is in the neighborhood of C.for Illinois coals, 110 C.

` for eastern bituminous coals and 160 C.` for semi-bituminous coalssuch as Pocahontas, it being understood that these temperature rangesinclude substantially all degrees of plasticity from the initial plasticcondition to the final condition involving partial formation of cokestructure. When coals having a relatively wide temperature range ofplasticity are treated, it is feasible to preheat the coal to such atemperature that at least some of the particles of the charge` arebrought into the initial plastic condition before the charge isdeposited into the coking oven. Since the swelling of the coal takesplace at and above the temperature of initial plasticity, this procedureavoids the swelling of the charge in the oven at least to some extent.Even though the charge is preheated up to the temperature at or abovethat at which the coal first becomes plastic, substantially all of theexothermic heat is liberated in the ovens and it is possible to obtaincoherent coke because the plastic condition persists long enough topermit the formation of a coherent mass in the ovens.

The above described heating of the coal i to a temperature at or abovethe critical temperature thereof before the coking operation commencesis set forth in our cepending patent application, Serial No. 5,499 ledJanuary 29, 1925.

Although the preheating temperature is preferably substantially uniformthroughout the mass of the coal charge, it should be understood thatcertain of the finer particles of the coal may reach temperaturesconsiderably higher than those attained by the coarser particles, andthe preheating temperatures explained above are therefore the averagetemperatures of the coal charge at the termination of the preheatingoperation.

The preheating operation is preferably carried out in such a manner thatthe coal attains the desired temperature within a limited period oftime. It has been found that if the time of preheating is undulyprolonged, certain reactions take place which prevent the elimination ofthe desired amount of deleterious oxygen and oxygen compounds. It istherefore preferred to preheat the coal to the desired temperaturequickly, and the preheating time should be preferably less than twohours.

According to one embodiment of the invention, the preheating of the coalis carrfed out in two successive stages, the raw coal being first heatedto a temperature equal to or slightly above the boiling point of water,and being subsequently heated, preferably in a separate container, tothe desired yfinal preheating temperature as explained above. The firstor .drying stage of the preheating treatment results in the removal offree moisture from the raw coal and raises the temperature thereof to avalue at or slightly above the boiling point of water, preferably atemperature of 100 C., whereas the second or conditioning stage resultsin the above elimination of oxygen and oxygen compounds, and furtherincreases the sensible heat of the coal. The drying operat'on isparticularly advantageous when the coal has been washed previous totreatment and by drying the coal in a separate container at acomparatively low temperature, the heating gases employed in thepreheating operation can be very economically utilized.

The process of the present invention results in the production of a cokehaving desirable characteristics unobtainable in ordinary by-productpractice. The coke obtained has an excessively high resistance tocrushing strain, is clean and highly orous, and is further characterizedby uni ormity in structure and quality throughout the mass of thecharge. This uniformity inthe character of the coke is probably due tothe above described autogenous progression of the ex- -othermicreactions throughout the charge which results in the fuel charge beingplastic and coherent throughout its mass. The coke as discharged fromthe ovens is characterized by the absence of the coking lines which areproduced in ordinary by-product practice.

The improved apparatus employed to carry out the process of theinvention includes suitable means for heating the coal out of contactwith the atmosphere to the desired preliminary temperature. According toone embodiment of the invention, this means comprises two separateheating devices which may be termed a drier and a conditioner. The drieris arranged to supply sufficient heat to the raw coal to drive off freemoisture and may conveniently comprise an inclined rotatable drum orcylinder through which the coal is tumbled and advanced while heat issuppliedthereto. Since the temperatures attained inthe drier arecomparatively low, the coal therein may be heated by direct Contact withsuitable heating ases, these gases preferably passing throu the drum ina direction opposite to that 1n which the coal progresses. Theconditioner is preferably arranged to heat the coal rapidly, and to thisend may conveniently comprise a closed cylinder or drum provided withsuitable means for suplying a controllable amount ofheat to the exteriorsurface thereof. In order that the coal may be agitated and so uniformlyheated in the conditioning device, the cylinder may be rotaied, or othermeans may be rovided for tumbling and advancing the el therein. The coalin the conditioner is preferably heated indirectly, and the hot gasesemployed for this purpose are preferably conducted along the outersurface of the conditioning drum in the same direction as that in whichthe coal progresses therethrough. The heating ases thus employed maycomprise waste ue gases from the ovens in which the coking process iscompleted, or a suitable fuel such as gas, oi l or coal, may be burnedto supply the required heat. The temperature of the gases employed toheat the conditioner is preferably variably adjustable by suitablemeans.

heated container or preheating device is satisfactory for use 1ncarrying out the process of the invention, it should be understood thatthis process is not limited to a device of this character and that thepreheating operation may be carried out by passing a heated fluidthrough a mass of quiescent coal, or various other means may be employedfor this purpose. Y

The apparatus for completing the coking process comprises a group orbattery of coke ovens in which the preheated coal is deposited and inwhich the coking operation proper is completed. The ovens preferablycomprise a unitary oven structure including adjacent oven chambersseparated by walls containing heating flues. The oven structure ispreferably formed of a suitable refractory material such as silica brickor fire-clay. The oven chambers may be of any suitable form, andmaycomprise horizontal ovens of the type commonly used in ordinaryby-product co ing practice. In the preferred form of the apparatus, theovens comprise long narrow chambers having removable doors at theiropposite ends, and provided with 'suitable-apparatus for pushing thecoke charge therefrom through one of these doors at the end of eachcoking operation. The ovens are preferably heated by burnin a suitablefuel such as producer gas wit in combustion chambers in the ovenstructure, and conducting the hot gases throu h the oven fines. The airfor sup orting combustion in the combustion cham ers is preferablypreheated by the waste fiue gases in suitable regenerators orrecuperators. v

Due to the above described evolution and flow of the hydrocarbon vaporsthroughout the mass of the coal charge Within the oven, the oven walltemperatures employed during the coking operation may be comparativelyhigh without causing undesirable cracking or decomposition of thehydrocarbons. Thus the oven wall temperatures may safely range from 750to l000 C. or even higher, the referred Wall tem erature being in thenelghborhood of 950 The final temperature of the coke char e may bevaried according to the type o coke desired. It has been found that asuperior quality of coke suitable for either domestic or metallurgicalpurposes can be made at final coke temperatures not exceeding 750 to 850C., the volatile content of this coke not being in excess of 5%. If alower volatile content is desired, the fuel charge may be allowed toremain in the oven for a longer period, without further materialincrease in the tempera- CTI Cil

j invention can best be understood byconsiderture of the charge. Suchprolongation of the coking time, even at temperatures of 750 to 850 C.,will have the effect of further reducing the volatile content andincreasing the temperature of reactivity, similar to corres ondingeffects obtained by employing higlber final coking temperatures butwithout producing the undesirable overcoking effects resulting from highfinal coking temperatures. The increase in the heating time produces aseasoning effect upon the coke without weakening the structure thereof.Since the oven walls are formed of refractory material, there is nodanger of injury to the walls as a result of the high temperatures whichthey may attain, and thus the structural difficulties encountered whenmetal retorts or ovens are employed are avoided. It has been found thatthe heat stored in the relatively massive walls of the ovens flows intothe coal charge rapidly and in sufficient amounts to complete the cokingprocess within a comparatively short time, such as three and one-half tosix hours.

When high oven wall temperatures are employed, a very thin crust orshell of coke may be formed adjacent the oven wall during the cokingoperation, and this shell may reduce the eiiiciency of heattransmissions to the coal to a certain extent. However, the high heathead established by the high wall temperature offsets the insulatingeffect of the coke shell and it is therefore possible to appreciablyreduce. the coking time by employing high temperatures, in spite of theformation of the coke shell. The formation of the coke shell does not inany way interfere with the above described autogenous progression ofexothermic reactions to the center of the coal charge. for the reasonthat this progression is not dependent upon the accession of extraneousheat. Accordingly, even when eX- tremely high oven wall temperatures areused, the coking takes place quite uniformly throughout the mass of thecharge, and the coke produced is of a uniform quality throughout anddoes not contain the coking lines, that is, lines of division betweenvarious grades of coke, which are characteristic of ordinary by-productpractice.

The ovens and the preheating apparatus are preferably located in closeproximity and suitable'rneans such as a lorry may be provided forcarrying the preheated coal from the preheater to the ovens. Thepreheater preferably operates continuously and has a capacity sufficientto supply several A oven chambers, the charges of preheated fuel beingaccumulated in the lorry. A small hopper or bin may be provided in whichthe preheated coal accumulates while the lorry is moved away from thepreheater to charge an Ove'n.

The various objects and advantages of the ing the accompanying drawingswhich show one embodiment of an improved apparatus by means of which theimproved rocess of l the invention may be performe In the drawings;

Figure 1 is a sectional elevation of the improved apparatus for carryingout the process of the invention;

Fig. 2- is an end view of the apparatus shown in Fig. 1; and

Fig. 3 is an elevation, taken along line 3 3 of Fig. 1, and showing thedriving gear of the preheating drum.

The embodiment of the preheating apparatus shown is of a type suitablefor bringing the raw coal to the desired preheating temperature in twostages, and comprises generally a drier D and a conditioner C. The driermay conveniently comprise a drum or cylinder 3 suitably rotatablysupported on the framework 4 and inclined toward the discharge end. Ahopper 5 and a screw conveyor 6 are preferably provided for introducingraw coal to the inlet end of the drier cylinder 3, the power foroperating the screw conveyor 6 and rotatingjthe drum 3 being supplied bysuitable means such as an electric motor (not shown) The gases forsupplyin heat to the coal in the drier are introduce at the dischargeend of the cylinder 3 through a hood 7, and are drawn olf through asimilar hood 8 at the inlet end of the cylinder. The conditioner Cpreferably comprises a rotatable inclined drum or cylinder 9 mountedwithin a heating chamber 10 which may be heat insulated and ispreferably provided` with a plurality of baiiles 11 for distributing theheating gases over the surfaces of the drum. The conditioner C iscarried by the supports'12 and 13, the support 12 being verticallyadjustable to vary the inclination of the drum and so regulate theadvance of the coal therethrough. The dried coal is fed into the upperor inlet end of the conditioner drum 9 from a chute 14 communicatingwith the hood 7 of the drier D, through'a power operated screw conveyor15. A suitable source of power such as an electric motor may be employedto rotate the conditioner drum 9 and the screw conveyor 15. A pluralityof blades 16, located within the discharge end of the conditioner drum9, serve to lift the preheated coal and drop it into a chute 17 leadingto a small hopper or bin 18. The lower end of the hopper 18 iscontrolled by a cut-off valve 19.

The inclined rotatable drum or cylinder 9 maybe rotated by any suitablemeans, and to this end, the inlet end thereof is provided with a drivinggear 50, as shown in Figs. 1 and 3.

The hot gasesl for heating the fuel in the conditioner C and the drier Dmay be supplied by any suitablev means. In the disclosed embodiment, asuitable fuel such as producer gas is burned in a furnace or combustionchamber 20, and the hot gases thus produced are conducted to theinterior of the heating chamber 10 through the pipe 21. The wasteheating gases from the conditioner are preferably supplied to theinterior of the drier cylinder 3 through the pipe 22. The temperature ofthe heating gases supplied to the conditioner is controlled byregulating the supply of the fuel at the burner 23, and by introducing avariable amount of air to the furnace 20 or to the stream of combusItion gases fiowing therefrom. It is pre4 ferred to introduce thehotgases to the conditioner heating chamber 10 at the inlet end of theconditioner drum 9, and thus deliver heat from the hottest gases to thecoolest portion of the coal charge in the conditionin drum. In thismanner, the overheating o the coal in the conditioner is avoided. Thewaste gases from the conditioner heating chamber 10 are passed throughthe drier cylinder 3 from the discharge end to the inlet end thereof,ina direction opposite to that F in which the coal progressestherethrough.

By utilizing the heating gases to successively heat the coal in theconditioner C and the drier D, the heat in these gases is economicallyutilized, the temperature of the gases leaving the drier being littleabove that of Vthe surrounding atmosphere. The rate of iiow of theheating gases throu h the conditioner and the drier is controlled y thedempers 24, 25 and 26. If desired, the conditioner C and the drier D maybe heated by waste flue gases from the coke ovens or from any othersource, or a combination of waste gases and supplemental burner gasesmay be emplo ed for this purpose. The waste gases may supplied to thepreheating ap aratus through the pipe 27, the rate of iow ereof beingcontrollable bythe damper 28.

The preheated coal is preferably discharged from the hopper 18 into -alorry or car 29 mounted on the tracks 30 and adapted to su ply thepreheated coal to any one of a plura ity of ovens 31. The lorry mayserve as an accumulatin bin for the preheated coal, the coal accum atingin the hopper 18 while the lorry is bein moved away to charge one of theovens. T e lorry is preferably of such dimensions that it can carryenough preheated coal to fill atleast one of the oven chambers 31.

The oven chambers 31 are preferably located within a unitary structure Oformed of suitable refractory material such as silica brick or fireclay. In the disclosed embodiment the oven structure includes four ovenchambers, but the number of these chambers may, of course, be varied tosuit the requirements of the installation. The ovens in the disclosedconstruction are of the horizontaltype, comprising narrow chambers ofconsiderably greater length than height. The chambers 31 able apparatus.A

are provided with suitable removable doors 32 at their opposite endsthrough which the finished coke charge may be pushed by suitlurality ofcharging ports 33 are provide in the upper wall of each oven chamber,these ports being normally closed by the caps or covers 34 and beingdisposed to align with the depending valve controlled dischar e ports 35of the lorry 29. The evolved hydrocarbon vapors are conducted from theovens through suitable up-take pipes 36 and are conducted throu happaratus for effecting the recovery og able constituents thereof.

The oven chambers 31 may be heated in any' convenient manner. The ovenheating apparatus shown is of a type ordinarily employed in by-productcoking practice, and since a paratus of this type is well known in t eart, the structure thereof Wil only be briefly described herein. Asshown in the drawings, the wall between each adjacent pair of ovenchambers 31 is provided with two sets of ues 37 and 38, havingcombustion chambers 39 `and 40 at the upper ends thereof respectively. Asuitable fuel such as producer gas is first admitted through thepassages 41 to the combustion chambers 39 at the upper ends of the flues37 ,f and heated air is supplied to these combustion chambers from aregenerator 42 through the passages 43 to support the combustion of thegas. The hot gases flow downwardly through the iiues 37 upwardly throughthe adjacent flues 38 and finally pass downwardly through ythe passage44 and through a regenerator 45 adjacent the regenerator 42, beingcarried therefrom to a stack through the tunnel 46. At suitable periods,the operation of the iues is reversed, fuel gas being admitted to thecombustion chambers 40 of the alternate flues 38 and the waste ue gasespassing out through the passages 43, the regenerator 42 and the tunnel47. In this manner, during successive operating periods, the adjacentregenerators 42 -and 45 alternately absorb heat from the waste ue anddeliver heat to the air supplied to the combustion chambers, and the'heat in the Waste flue gases is thereby conserved. c

In carrying out the improved process by means of the apparatusillustrated in the drawings, the raw coal is first delivered in crushedform to the cylinder 3 of the drier D through the conveyor 6. Within thedrier, the raw coal is tumbled and advanced in direct contact withheating gases and is quickly raised to or slightly above the boilingpoint of water. In the drier, the free moisture in the raw coal isdriven ofi', and the temperature of the coal is raised to a valuepreferably between 100 and 120 C. The dried coal passes through thechute 14 and the conveyor 15 to the drum 9 of the conditioner C, and isindirectly heated therein, out of contact with the atmosphere, to therethe valuquired preheating temperature. s Vhereinbefore explained, thefinal temperature to which the coal is heated in the conditioner shouldbe at least high enough so that the exothermic heat subsequently madeavailable in the coal is suiicient of itself to heat the coal from thistemperature to or above the temperature at which the exothermicreactions begin, thereby insuring the autogenous progression ofexothermic reactions throughout a charge of this preheated. coal duringits subsequent treatment in the ovens. Since the coal is agitated by therotation of the conditioner drum 9, it is heated substantially uniformlythroughout and at a rapid rate. The preheating of the coal in the drierand the conditioner may be completed in a very short time, and shouldnot consume more than two hours. The preheating conditions the coal bydriving ofi' water vapor, oxygen, oxygen compounds and other materialswhich should be removed before the coal is subjected to cokingtemperatures in order to cut down the coking time and improve theproducts obtained. As explained above, the preheated coal is accumulatedin the lorry 29 and is subsequently discharged into the oven chambers31, the walls of which have been previously preheated to a temperaturebetween 750 and 1000O C., or even higher, this initial wall temperaturepreferably being in the neighborhood of 950 C.

The portion of the preheated coal charge which lies adjacent the ovenwalls is quickly raised by extraneous heat from these walls to atemperature above that at which exothermic reactions are initiated, andthe heat liberated by these exothermic reactions raises the temperatureof the adjacent portions of the coal charge to and above the point atwhich exothermic reactions take place therein. In this manner, theexothermic reactions progress rapidly and autogenously to the center ofthe fuel mass, and the entire charge is quickly brought to a plastic andcoherent condition throughout. The progress of the plastic conditionthrough the charge is accelerated by theevolved hydrocarbon gases whichcarry heat to the central portions of the charge as they iow upward tothe oven. Since the hydrocarbon vapors are simultaneously evolvedthroughout the coal charge and are not confined by a plastic envelope tothe outer portions thereof adjacent the hot oven walls, these vapors arewithdrawn from the ovens without being subjected to crackingtemperatures and substantially no heat is absorbed from the charge bysecondary decompositions of this nature.

Y The coking operation proceeds until the desired coking temperature isobtained whereupon the doors 32 of the oven chamber are opened and thecoke charge is pushed out by suitable means. A final coking temperatureof from750 to 850 C. has been found to result in the production of agood grade of coke for domestic or metallurgical purposes, the volatilecontent of the coke thus produced being not in excess of 5%. Due to theconditioning operation employed, the entire coking operation can becompleted in from four' to six hours. When coke of lower volatilecontent is desired, the coke charge is permitted to remain in the ovenfor a longer period, such prolongation of the coking time resulting in areduction of the volatile content of the coke and an increase in thetemperature of reactivity thereof, even though the final cokingtemperature is not materially increased. AThe process of the inventionis thus'quite flexible, it being possible to produce coke of any desiredvolatile content by simply varying the time period during which thecharge remains in the oven. Although as explained above, coke of verylow volatile content may be produced at low final temperatures, theprocess of the present invention is not limited to such temperatures andin certain cases the coking temperatures `may reach values from 950 to10000 C. or

even higher. Regardless of the final coke temperatures attained, theprocess of the invention results in the above noted advantages such asthe uniformity of the coke structure, the value and uniformity of thetar and gas produced, and the economy in heat and time consumed, theseadvantages being largely due to the manner in which the fuel is heatedup to and through the plastic stage, and to the above describedutilization of the exothermic heat available in the coal.

When the coal is preheated to a temperature at or slightly above thecritical temperature of the coal, a certain amount of the swellingincident to the plastic stage takes place within the conditioner C, andthe swelling of the charge in the oven chambers is thereby appreci ablyreduced.

From the foregoing description of the invention it will be apparent thatby employing the preheating operation described, the coal may be cokedin a very economical manner. Not only is the coking time appreciablyreduced, but certain other disadvantages, formerly consideredinevitable, in b v-product practice, are largely eliminated. Thus thesticking of the coal charge in the oven is avoided, the evolvedhydrocarbons are not cracked or decomposed in escaping from the ovens,and the coke produced is of a uniform and desirable character throughoutthe charge.

It is to be understood that the described process and apparatusmay bevaried without departing from the spirit of the invention which is notlimited to the particular embodiments illustrated and described. butincludes all such modifications thereof as fall Within the scope of theappended claims. For example, while it is preferred to use the t pe ofreheating apparatus described, other evices y which coal can beuniformly heated to the desired preliminarytemperatures ma be employed.e claim:

1. The process of coking coal which comprises heating the coal uniformlythroughout and with agitation out of contact W'th the atmosphere toatemperature below the minimum temperature at which exothermic reactionsare initiated in the absence of air but high enough so that theexothermic heat available in the coal from exothermic reactions in theabsence of air. is sufficient to bring the coal from such temperature toat least a temperature at which exothermic reactions are initiated inthe absence of air, depositing a charge of the preheated coal inaan ovenand supplying sufficient extraneous heat to the coal in the oven tobring at least a portion of said charge to the minimum temperature atwhich exothermic reactions are initiated in the absence of air and tocoke the coal.

2. The process of coking coal which comprises heating the coal withagitation and y uniformly throughout in anv air excluding container to atemperature below the minimum temperature at which exothermic reactionsare initiated in the absence of air but high enough so that theexothermic heat available in the coal from exothermic reactions in theabsence of air is sufficient to bring the coal from such temperature toat least the minimum temperature at which exothermic reactions areinitiated in the absence of air, depositing a charge of the preheatedcoal in an oven, and supplying sufiicient extraneous heat to the coal inthe oven to coke the coal.

3. The process of coking coal which comprises heating the coal uniformlythroughout and with agitation in an air excluding container to atemperature below the mini.- mum temperature at which exothermicreactions are initiated in the absence of air but high enough so thatthe exothermic heat available in the coal from exothermic reactions inthe absence of air is suicient to bring the coal from such temperatureto at least the minimum temperature at which exothermic reactions areinitiated in the absence of air, depositing a charge of the preheatedcoal in an oven, and supplying sufficient extraneous heat to coke thecoal in the oven at a final temperature of at least 750 C.

4. The process of coking coal which comprises heating the coal uniformlythroughout and with agitation in an air excluding container to atemperature below the minimum temperature at which exothermic reactionsare initiated in the absence of air but high enough so that theexothermic heat available in the coal from exothermic reactions in theabsence of air is suiicient to bring the coal from such temperature toat least the minimum temperature at which exothermic reactions areinitiated in the absence of air, and coking the coal by depositing acharge of the preheated coal in an oven having its Walls reviouslyheated to a temperature between 50 and 1000 C.

5. The process of coking coal which comprises heating the coal uniformlythroughout out o f-contact with the atmosphere and with agitation to atemperature high enough to insure the autogenous progression ofIexothermic reactions throughout a charge of the preheated coal when aportion thereof is heated to a temperature at which exothermic reactionsare initiated, depositing a charge ofthe preheated coal in lan ovenhaving its walls previously heated to a temperature of at least 750 C.and supplying sufficient extraneous heat to the coal charge in the ovento bring at least a portion of said charge to a temperature at whichexothermic reactions take place and to coke the coal.

6. The process of coking coal which comprises heating the coal uniformlythroughout out of contact with the atmosphere and with agitation to atemperature high enough to insure the autogenous progression ofexothermic reactions throughout a chargeJ of the preheated coal when aportion thereof is .heated to a temperature at which exothermicreactions are initiated, and coking the coal by depositing the coal inan oven having its walls previously heated to a temperature ofapproximately 950 C.

e process of cokin coal which comprises heating the coal uni ormlythroughout out of contact with the atmosphere and with agitation to atemperature high enough to insure the autogenous progression ofexothermic reactions throughout a charge of the preheated coal when aportion thereof is heated to a temperature-at which exothermic reactionsare initiated, depositing the coal in an oven having its wallspreviously heated to a temperature of approximately 950 C. and supplyingsuicient extraneous heat to the coal in the oven to 'coke the coal at afinal temperature above 750 C.

8. The process of coking coal which comprises heating the coal uniformlythroughout out of contact with the atmosphere and with agitation to atemperature high enough to insure the autogenous rogression ofexothermic reactions throug out a charge of the preheated coal when aportion thereof is heated tota temperature at which exothermic reactionsare initiated, depositing the coal in an oven having its wallspreviously heated to a temperature of approximately 950 C. and supplyingsucient extraneous heat to the coal in the oven to coke the coal at afinal temperature in the neighborhood of 950 C.

9. The process of coking coal which comprises uniformly heating the coalout of contact with the atmosphere and with agitation to a temperaturebetween a value close to the critical temperature ofthe coal and a lowervalue high enough to insure the autogenous progression of exothermicreactions throughout a charge of the preheated coal when a portionthereof is heated to a temperature at which exothermic reactions areinitiated, depositing a charge of the preheated coal in an oven andsupplying sufficient extraneous heat to the coal charge in the oven tobring at least a portion of said charge to a temperature at whichexothermic reactions take place and to coke the coal.

l0. The process of coking coal which coniprises uniformly heating the.coal out of contact with the atmosphere and with agitation to atemperature between a value close to the critical temperature of thecoal and a lower value high enough to insure the autogenous progressionof exothermic reactions throughout a charge of the preheated coal when aportion thereof is heated to a temperature at which exothermic reactionsare initiated, depositing a charge of the preheated coal in an oven, andsupplying sufficient extraneous heat to the coal charge in the oven tobring at least a portion of said charge to a temperature at whichexothermic reactions take place, and to coke the coal at a finaltemperature in the neighborhood of 950 C.

11. The process of coking coal which comprises heating the raw coal to atemperature of from 100 to 120 C. by direct contact with heating gases,indirectly heating the coal uniformly throughout and with agitation fromsuch temperature to a temperature high enough to insure the autogenousprogression of exothermic reactions throughout a charge of the preheatedcoal when a portion thereof is heated to a temperature at whichexothermic reactions are initiated, and coking the coal by depositing acharge of the coal in an oven having its walls previously heated to atemperature above 7 50 C. i

12. The process of coking coal which comprises heating the coaluniformly throughout in an air excluding container and with agitation toa temperature not appreciably higher than the critical temperatureof thecoal but high enough t0 insure a material reduction in the oxygencontent of the coal, depositing a. charge of the coal so heated in anoven, supplying sufficient heat to the coal in the oven to convert thecharge into coke at a final temperature above 650 C., and maintainingthe coke in the oven without substantial increase in the temperaturethereof over the said final value until the volatile content of the cokehas been reduced below the value of volatile content at the time thatthe said final temperature is first attained.

13. The process of coking coal which comprises heating the coaluniformly throughout in an air excluding container and with agitation toa temperature not appreciably higher than the critical temperature ofthe i coal but high enough to insure a material reduction in the oxygencontent of the coal, depositing a charge of the coal so heated in anoven, supplying sufficient heat to the coal in the oven to convert thecharge into coke at a final temperature above 650 C. and maintaining thecoke in the oven' without substantial increase in the temperaturethereof over the said final value until the temperature of reactivity ofthe coke has been increased to a value higher than the temperature ofreactivity of the coke at the time that the said final temperature isfirst attained.

14. The process of coking coal which com prises heating the coaluniformly throughout in an air excluding container and with agitation toa temperature not appreciably higher `than the critical temperature ofthe coal but high enough to insure a material reduction in the oxygencontent of the coal, depositing a charge of the coal so heated in anoven, supplying sufficient heat to the coal in the oven to convert thecharge into coke at a final temperature of above 750 C. and maintainingthe coke in the oven without substantial increase in the temperaturethereof over the said final value until the volatile content of the cokehas been reduced below the value of volatile content existing at thetime that the said final temperature is first attained.

In testimony whereof we affix our signatures.

SAMUEL W. PARR. THOMAS E. LAYNG.

